Hard disk drives are used in almost all computer system operations, and recently even in consumer electronic devices such as digital cameras, video recorders, and audio (MP3) players. In fact, most computing systems are not operational without some type of hard disk drive to store the most basic computing information such as the boot operation, the operating system, the applications, and the like. In general, the hard disk drive is a device which may or may not be removable, but without which the computing system will generally not operate.
The basic hard disk drive model was established approximately 50 years ago. The hard drive model includes a plurality of storage disks or hard disks vertically aligned about a central core that can spin at a wide range of standard rotational speeds depending on the computing application in which the hard disk drive is being used. Commonly, the central core is comprised, in part, of a spindle motor for providing rotation of the hard disks at a defined rotational speed. A plurality of magnetic read/write transducer heads, commonly one read/write transducer head per surface of a disk, where a head reads data from and writes data to a surface of a disk, are mounted on actuator arms.
Data is formatted as written magnetic transitions (information bits) on data tracks evenly spaced at known intervals across the disk. An actuator arm is utilized to reach out over the disk to or from a location on the disk where information is stored. The complete assembly at the extreme of the actuator arm, e.g., the suspension and magnetic read/write transducer head, is known as a head gimbal assembly (HGA).
In operation, pluralities of hard disks are rotated at a set speed via a spindle motor assembly having a central drive hub. Additionally, there are channels or tracks evenly spaced at known intervals across the disks. When a request for a read of a specific portion or track is received, the hard disk drive aligns a head, via the actuator arm, over the specific track location and the head reads the information from the disk. In the same manner, when a request for a write of a specific portion or track is received, the hard disk drive aligns a head, via the actuator arm, over the specific track location and the head writes the information to the disk.
Particularly, there is a tracing, also commonly referred to as a flexure, which is part of a suspension, that communicatively couples the read/write head or slider assembly with the tail portion of the actuator arm upon which a HGA is mounted. The tracing is commonly routed along the midline of the suspension, altered so that the tracing is routed in a direction perpendicular to the midline, and then altered again to parallel the midline but having a location toward an outer edge of the suspension. This type of traces routing is asymmetric. The asymmetry can create a twisting force on the hinges when the suspension is under dynamic loading such as shock and windage. This can also cause a mass imbalance by virtue of the traces and the flexure stainless steel disposed outside of the hinges, e.g., away from the centerline of the suspension. For example, during operation of the hard disk drive, the flexure is subject to windage, e.g., generated airflow within a hard disk drive, generated by the operation of the hard disk drive. When windage affects the flexure, the flexure can cause improper functioning of the suspension of which it is a part as well as the read/write head mounted on the suspension.
Prior art FIG. 7 is an illustrated image of a suspension and a tracing that depicts an effect of windage during operation of a hard disk drive. FIG. 7 shows a suspension having a transducer (read/write head) 8 mounted to a load beam 26. The suspension further includes a mount plate 23, a hinge plate 25 and a flexure 77. In the image shown in FIG. 7, flexure 77 is shown to have a bending and twisting motion in one of its natural frequency mode shapes. Laser welding is commonly, but not always, utilized for affixing a flexure 77 to a load beam 26. Conventionally, laser welding of a tracing is commonly, but not always, accomplished generally at weld points 41 and 42. As shown in FIG. 7, a portion of flexure 77 has lifted or separated from the load beam 26 during operation of the hard disk drive and as a result of windage. This separation or lifting can cause a rotational force to be applied to the suspension, thus causing a twisting of the hinge or the load beam or a combination thereof. This twisting motion can cause an increase in off-track motion of the slider of the suspension under windage. Off-track motion can increase instances of NRRO (non-repeatable run out) and TMR (track mis-registration).
A solution for the reduction of separation or lifting of the tracing from the suspension and/or off-track motion caused by windage was to implement additional welds to anchor the free span of the flexure between weld points at 43 and 44. However, additional welds are not without certain drawbacks. Additional welds inherently increase the stiffness of the suspension which can have a detrimental affect upon the suspension's ability to properly flex and function during hard disk drive operation.
Another solution was to re-route a tracing from that of FIG. 2 to that of FIG. 3. In FIG. 2 the tracing of the flexure 287 goes outside of the load beam just before the hinges 225. The tracing then is routed alongside the hinges and mount plate 223. The bending and twisting motion of the tracing along side the hinges under dynamic loading such as shock and windage can cause substantial off track motion of the slider in this design. In FIG. 3 the situation is improved by routing the tracing so that it goes through the center of the two hinges 325. In doing so, the off track motion of the slider can be reduced when the tracing is twisting and bending under dynamic loading such as shock and windage.
With reference to both FIGS. 8 and 9, there is, inherent to both tracings, a dynamic that can be described by mass and stiffness or rigidity.
FIG. 8 is an illustration of the stainless steel portion of a conventional single serpentine tracing, implementable upon a suspension susceptible to windage effects during operation of a hard disk drive. Serpentine tracing 87 includes an end 82 that is oriented toward a slider, e.g., slider 8 of FIG. 7, and an opposing end 83 that is to be oriented toward a tail of an actuator arm to which a suspension upon which tracing 87 is disposed. Serpentine tracing 87 further includes a turning portion that changes the direction of tracing 87 from a direction that is parallel to the midline of the suspension, upon which tracing 87 is mounted, so as to relocate tracing 87 such that tracing 87 parallels the midline of the suspension but is now located proximal to an outer edge of the suspension. Tracing 87 is shown to have a plurality of bridges 86.
However, a single serpentine tracing having a layer of stainless steel as shown is not without certain drawbacks. For example, the physical characteristics of tracing 87 are such that an outer portion 88 of the turning portion is less rigid than an inner portion 89 of the turning portion. By virtue of outer portion 88 being less rigid that inner portion 89, tracing 87 can have twisting motion as it bends under dynamic loadings as shown in FIG. 7.
FIG. 9 is an illustration of the stainless steel portion of a conventional dual-serpentine tracing, implementable upon a suspension susceptible to windage effects during operation of a hard disk drive. Dual-serpentine tracing 97 includes an end 92 that is oriented toward a slider, e.g., slider 8 of FIG. 7, and an opposing end 93 that is to be oriented toward a tail of an actuator arm to which a suspension upon which tracing 97 is disposed. Serpentine tracing 97 further includes a turning portion that changes the direction of tracing 97 from a direction that is parallel to the midline of the suspension, upon which tracing 97 is mounted, so as to relocate tracing 97 such that tracing 97 parallels the midline of the suspension but is now located proximal to an outer edge of the suspension. Tracing 97 is shown to have a plurality of bridges 96.
Similarly, a dual-serpentine tracing having a stainless steel portion as shown is not without similar drawbacks same as the single serpentine. The physical properties of conventional dual-serpentine tracing 97 are such that an outer dual-serpentine portion 98 of the turning portion is less rigid than an inner dual-serpentine portion 99 of the turning portion. By virtue of outer dual-serpentine portion 98 being less rigid than inner dual-serpentine portion 99, tracing 97 is susceptible to effects of windage same as the single serpentine design.
Therefore, a need exists for a tracing that includes the functionality of a serpentine design while increasing resistance against torsion, rotation and off-track motion caused by windage (air-flow) present during hard disk drive operation.